Existing inspection systems and methods for the inspection of surfaces and surface coatings (collectively, “surfaces” as used herein) may suffer from many drawbacks. This is particularly true when the surface to be inspected is fairly large (such as an aircraft) and the spectrum of electromagnetic radiation on the surface may vary with the environment (e.g., indoor versus outdoor).
For example, when painting aircraft it is often common to mix mica into the paint, or to apply a mica coating over the aircraft surface. Uneven mixing or application of the mica can leave the aircraft with a spotted or mottled appearance. This mottling may be difficult to observe under the indoor lighting used in the painting facility and often the mottled appearance does not show until the painting is complete and the aircraft is observed outdoors under natural daylight. It then can be problematic and expensive to re-apply paint or other coatings to alleviate the mottling or other visual defect.
Some existing systems, such as Laser Scanning Confocal Microscopy (LSCM) may be used to inspect surfaces and evaluate whether a defect such as mottling exist, however, performance of LSCM is often a tedious and local measurement that requires access to the plane.
Another proposed solution has been to add lamps to the interior of a structure housing an airplane. Then the aircraft could be painted, or at least inspected, under such lighting. Potential drawbacks of this approach include the relatively high cost of a large scale illumination system, and that the orientation of illumination and imaging is not controlled (i.e., the illumination is primarily from above on the top side of the aircraft) which can leave defects on the underside surfaces undetected. In addition, large scale illumination systems like the above-described one are not practical for inspecting surfaces for defects that are not visible to the human eye (e.g., surface features that require infrared, ultraviolet, or other spectra to observe). Other drawbacks may also exist.
Another potential drawback of existing systems for surface inspection is that it is often difficult to relate inspected surface information to a location on the aircraft, or larger overall surface, for later remediation. For example, when using hand-held imaging tools, the location of the particular defect is not automatically located on the larger surface and requires additional marking or logging of the location of the defect. Other drawbacks may also exist.
Another potential drawback of existing systems is that for irregular, curved, or other non-simple surfaces, it is often difficult to ensure that the angle of incidence for the inspection illumination is at the desired angle of incidence, likewise with the angle of observation of the imaging device (e.g., camera). Improper angle of incidence or observation can yield faulty inspection results. Other drawbacks may also exist.